#include <iostream>
#include <fstream>
#include <deque>
#include <set>
#include <algorithm>
#include <stack>
#include <vector>
#include <iomanip>

#define x first
#define y second

#define MAX 120005

using namespace std;

ifstream fin("infasuratoare.in");
ofstream fout("infasuratoare.out");

int n;
pair<int, int> v[MAX];
pair<int, int> S[MAX];
int head;

void read() {
	fin >> n;
	for (int i = 1; i <= n; ++i)
		fin >> v[i].x >> v[i].y;
}

double crossfit(const pair<int, int>& A, const pair<int, int>& B, const pair<int, int>& C) {
	return (B.x - A.x) * (C.y - A.y) - (B.y - A.y) * (C.x - A.x);
}

int cmp(const pair<int, int>& p1, const pair<int, int>& p2) {
	return crossfit(v[1], p1, p2) < 0;
}

void sort_points() {
	int pos = 1;
	for (int i = 2; i <= n; ++i)
		if (v[i] < v[pos])
			pos = i;
	swap(v[1], v[pos]);
	sort(v + 2, v + n + 1, cmp);
}

void convex_hull() {
	sort_points();

	S[1] = v[1];
	S[2] = v[2];

	head = 2;

	for (int i = 3; i <= n; ++i) {
		while (head >= 2 && crossfit(S[head - 1], S[head], v[i]) > 0)
			--head;
		S[++head] = v[i];
	}
}

void write() {
	fout << fixed;
	fout << head << "\n";
	for (int i = head; i >= 1; --i)
		fout << setprecision(9) << S[i].x << " " << S[i].y << "\n";
}

int main() {
	read();
	convex_hull();
	write();

	return 0;
}